III. Solutions
Apply patches
All users are encouraged to apply the patches referred to in
Microsoft Security Bulletin MS03-026
as soon as possible in order to mitigate the vulnerability described in VU#568148. These patches are also available via Microsoft's
Windows Update
service.
Systems running Windows 2000 may still be vulnerable to at least a
denial of service attack via VU#326746 if their
DCOM RPC service is available via the network. Therefore, sites are
encouraged to use the packet filtering tips below in addition to
applying the patches supplied in MS03-026.
Filter network traffic
Sites are encouraged to block network access to the RPC service at
network borders. This can minimize the potential of denial-of-service
attacks originating from outside the perimeter. The specific services
that should be blocked include
- 135/TCP
- 135/UDP
- 139/TCP
- 139/UDP
- 445/TCP
- 445/UDP
If access cannot be blocked for all external hosts, the CERT/CC
recommends limiting access to only those hosts that require it for
normal operation. As a general rule, the CERT/CC recommends filtering
all types of network traffic that are not required for normal
operation.
Because current exploits for VU#568148 create a
backdoor, which is in some cases 4444/TCP, blocking inbound TCP
sessions to ports on which no legitimate services are provided may
limit intruder access to compromised hosts.
Recovering from a system compromise
If you believe a system under your administrative control has been
compromised, please follow the steps outlined in
- Steps
for Recovering from a UNIX or NT System Compromise
Reporting
The CERT/CC is tracking activity related to exploitation of the
first vulnerability (VU#568148) as
CERT#27479 and the second vulnerability (VU#326746) as
CERT#24523. Relevant artifacts or activity can be sent to
cert@cert.org with the appropriate CERT# in the subject line.
Appendix A. Vendor Information
This appendix contains information provided by vendors. When vendors
report new information, this section is updated and the changes are
noted in the revision history. If a vendor is not listed below, we
have not received their comments.
